Tolerances of the Human Brain to Concussion FAACivil Aeromedical Institute, Oklahoma/City

Swearingen, John J.

doi:10.1515/bmte.1972.17.2.57

Cited by 4 publications

(4 citation statements)

References 7 publications

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“…Anthropometric studies have demonstrated that the CoM of quietly standing humans lies approximately a few centimeters in front of the lumbosacral joint, about 57% of the body height from the feet plants, in both children and adults (15). Sophisticated modeling has allowed the estimation of its location in various postures and during various motor tasks; again, in children (15) and in adults (16, 17). Tracking the CoM during walking, however, is much more difficult.…”

Section: Modeling the Walking Phenomenonmentioning

confidence: 99%

The Motion of Body Center of Mass During Walking: A Review Oriented to Clinical Applications

2019

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Human walking is usually conceived as the cyclic rotation of the limbs. The goal of lower-limb movements, however, is the forward translation of the body system, which can be mechanically represented by its center of mass (CoM). Lower limbs act as struts of an inverted pendulum, allowing minimization of muscle work, from infancy to old age. The plantar flexors of the trailing limbs have been identified as the main engines of CoM propulsion. Motion of the CoM can be investigated through refined techniques, but research has been focused on the fields of human and animal physiology rather than clinical medicine. Alterations in CoM motion could reveal motor impairments that are not detectable by clinical observation. The study of the three-dimensional trajectory of the CoM motion represents a clinical frontier. After adjusting for displacement due to the average forward speed, the trajectory assumes a figure-eight shape (dubbed the “bow-tie”) with a perimeter about 18 cm long. Its lateral size decreases with walking velocity, thus ensuring dynamic stability. Lateral redirection appears as a critical phase of the step, requiring precise muscle sequencing. The shape and size of the “bow-tie” as functions of dynamically equivalent velocities do not change from child to adulthood, despite anatomical growth. The trajectory of the CoM thus appears to be a promising summary index of both balance and the neural maturation of walking. In asymmetric gaits, the affected lower limb avoids muscle work by pivoting almost passively, but extra work is required from the unaffected side during the next step, in order to keep the body system in motion. Generally, the average work to transport the CoM across a stride remains normal. In more demanding conditions, such as walking faster or uphill, the affected limb can actually provide more work; however, the unaffected limb also provides more work and asymmetry between the steps persists. This learned or acquired asymmetry is a formerly unsuspected challenge to rehabilitation attempts to restore symmetry. Techniques of selective loading of the affected side, which include constraining the motion of the unaffected limb or forcing the use of the affected limb on split-belt treadmills which impose a different velocity and power to either limb, are now under scrutiny.

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Section: Modeling the Walking Phenomenonmentioning

confidence: 99%

The Motion of Body Center of Mass During Walking: A Review Oriented to Clinical Applications

2019

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“…We use the SVD of the measurement matrix as a means of quantitatively assessing the cross-range measurement capacity of the system, considering a cross-range slice of 2 m 2 in the scene at a distance of 1 meter. This area exceeds the estimated average cross-section of a person 36 , roughly 0.75 m 2 . Figure 3(A) shows the singular value spectrum of the frequency-diverse metasurface system prototyped here, and for comparison, a similarly sized monostatic SAR system.…”

Section: Resultsmentioning

confidence: 69%

Large Metasurface Aperture for Millimeter Wave Computational Imaging at the Human-Scale

Gollub

Yurduseven

Trofatter

et al. 2017

Sci Rep

221

136

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We demonstrate a low-profile holographic imaging system at millimeter wavelengths based on an aperture composed of frequency-diverse metasurfaces. Utilizing measurements of spatially-diverse field patterns, diffraction-limited images of human-sized subjects are reconstructed. The system is driven by a single microwave source swept over a band of frequencies (17.5–26.5 GHz) and switched between a collection of transmit and receive metasurface panels. High fidelity image reconstruction requires a precise model for each field pattern generated by the aperture, as well as the manner in which the field scatters from objects in the scene. This constraint makes scaling of computational imaging systems inherently challenging for electrically large, coherent apertures. To meet the demanding requirements, we introduce computational methods and calibration approaches that enable rapid and accurate imaging performance.

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“…As participants moved their arms at a comparable speed to the CoM (Fig. 8 ), rather than using the swing to create extensive, additional momentum as is often done to increase height in jumps 119 , 120 , they probably used their arms to shift the CoM anteriorly 121 . This possibly helps to hold the CoM as long as possible over the pads (CoM-heel angle ≈ 0°) in the exaggerated forward leaning strategy.…”

Section: Discussionmentioning

confidence: 99%

Rollator usage lets young individuals switch movement strategies in sit-to-stand and stand-to-sit tasks

Herzog,

Krafft,

Stetter

et al. 2023

Sci Rep

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The transitions between sitting and standing have a high physical and coordination demand, frequently causing falls in older individuals. Rollators, or four-wheeled walkers, are often prescribed to reduce lower-limb load and to improve balance but have been found a fall risk. This study investigated how rollator support affects sit-to-stand and stand-to-sit movements. Twenty young participants stood up and sat down under three handle support conditions (unassisted, light touch, and full support). As increasing task demands may affect coordination, a challenging floor condition (balance pads) was included. Full-body kinematics and ground reaction forces were recorded, reduced in dimensionality by principal component analyses, and clustered by k-means into movement strategies. Rollator support caused the participants to switch strategies, especially when their balance was challenged, but did not lead to support-specific strategies, i.e., clusters that only comprise light touch or full support trials. Three strategies for sit-to-stand were found: forward leaning, hybrid, and vertical rise; two in the challenging condition (exaggerated forward and forward leaning). For stand-to-sit, three strategies were found: backward lowering, hybrid, and vertical lowering; two in the challenging condition (exaggerated forward and forward leaning). Hence, young individuals adjust their strategy selection to different conditions. Future studies may apply this methodology to older individuals to recommend safe strategies and ultimately reduce falls.

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Tolerances of the Human Brain to Concussion FAACivil Aeromedical Institute, Oklahoma/City

Cited by 4 publications

References 7 publications

The Motion of Body Center of Mass During Walking: A Review Oriented to Clinical Applications

The Motion of Body Center of Mass During Walking: A Review Oriented to Clinical Applications

Large Metasurface Aperture for Millimeter Wave Computational Imaging at the Human-Scale

Rollator usage lets young individuals switch movement strategies in sit-to-stand and stand-to-sit tasks

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